The present invention relates to a receiver circuit, an electronic instrument, and a signal processing method.
In an electronic instrument including a receiver circuit, an alternating current signal may be generated due to a change in electromagnetic field accompanying the circuit operation of an electronic circuit disposed near the receiver circuit. The alternating current signal may be transmitted to the receiver circuit and mixed into the received signal as an interference wave. Such a phenomenon causes a significant signal deterioration. Therefore, various technologies have been proposed to remove an interference wave superimposed on a received signal.
For example, JP-A-2006-145315 discloses technology which reverses the phase of a signal generated by an electronic circuit using a delay line to generate a signal (hereinafter referred to as “cancellation signal”) which cancels the generated signal, thereby removing an interference wave.
A signal received by a reception section such as an antenna is a weak signal. Therefore, it is a common practice to increase the signal level of the received signal by amplification and process the amplified signal. According to the technology disclosed in JP-A-2006-145315, a contact point of the delay line is provided at a position in the middle of a signal line which connects the antenna and the signal processing system in the preceding stage of the amplification stage, and the cancellation signal is added to a weak signal immediately after reception.
Therefore, it is necessary to appropriately cancel the interference wave component mixed into the weak received signal by accurately controlling the signal level of the cancellation signal added to the received signal. If the signal level of the cancellation signal is inappropriate, the interference wave component may increase due to the cancellation signal having a signal level exceeding a signal level sufficient to cancel the interference wave component, whereby the reception sensitivity may deteriorate.